Astronomers: Earth and the moon had a common source of water

Like detectives trying to solve a 4.5 billion year-old mystery, astronomers have found another clue about the formation of Earth and the moon — they share a common source of water.

A giant impact? (WikiMedia)

The finding sheds light on the so-called giant-impact hypothesis, which suggests that the moon was formed out of the debris left over from a collision between Earth and another body the size of Mars.

Today’s finding concerns the nature of water on both the Earth and the moon.

Publishing today in the journal Science (see abstract), astronomers describe their study of volcanic glass inside moon rocks that were brought back to Earth by NASA’s Apollo 15 and 17 missions.

The scientists looked at features in the rock known as “melt inclusions,” which are tiny bits of glass found within crystals in lunar rocks. Water can be trapped in these inclusions. Using sophisticated probes, the astronomers were able to study the molecular signature of the moon’s water and match it to that found in carbonaceous chondrites, or meteorites found in the asteroid belt.

This indicates the the source of water is meteorites from the early epoch of the solar system, which is also believed to be a source of water on Earth as it was being formed.

Taking their analysis a step further, the astronomers say the most likely explanation is this: There was water on the early Earth before the giant impact some 4.5 billion years ago, and that some of the water that was there could have been taken with the “moon” when it formed as a result of this titanic collision.

Of course no one was around billions of years ago to tell us what really happened. But I think it’s pretty darn cool that new tools and techniques are allowing us to glean insights from rocks brought back from the moon four decades ago.